Method and apparatus for chromatic dispersion compensation and dispersion slope compensation in wavelength division multiplexed systems utilizing a channel separator and virtually imaged phased arrays

The present invention provides a method and apparatus for an improved chromatic dispersion compensator. In an apparatus aspect, the present invention includes a channel separator for separating a wavelength division multiplexed light comprising a plurality of channels, the plurality of channels containing undesired chromatic dispersion and dispersion slope; and a plurality of partial-channel-set dispersion compensation devices optically coupled to the channel separator in a cascade arrangement, wherein each partial-channel-set dispersion compensation device includes: a virtually imaged phased array (VIPA) optically coupled to the channel separator, and a light returning device optically coupled to the VIPA, wherein a combination of the VIPA and the light returning device compensates for the undesired chromatic dispersion and dispersion slope by propagating each wavelength of the plurality of channels along a different path length. The controlled difference between the periodicity of each VIPA's group delay response and the periodicity of the channel spacing causes the light of each channel input to the VIPA to acquire a different value of chromatic dispersion from that of every other channel input to the same VIPA, which is utilized so as to compensate dispersion slope. Advantages in using this chromatic dispersion compensator includes tunability, adaptability to various fiber types or optical transmission regions with either positive or negative dispersion, smaller size and lower cost. Also, the present invention provides the capability of simultaneously providing different values of dispersion compensation to different channels, i.e., it is capable of correcting for dispersion slope.